Microkeratome blades are now widely used for in situ ophthalmic surgeries employing laser correction. In such surgical systems, the eye is drawn into a fixed exposed position so that a cutting blade can move in a curved or linear path across the cornea, tangential to the curve of the eye, and at a preselected depth. The blade thereby cuts a flap of controlled thickness in the cornea across the center of the eye. The flap can then be raised, so that a computer controlled laser beam can be directed against the exposed portion and corneal tissue selectively ablated to introduce the needed optical correction. The flap is then returned back into position on the principal body of the cornea and no further surgical treatment such as a suture is typically needed. 
The blades used in these operations are small (about ½ inch in cutting edge length) and are formed as an integrated unit with a small holder or driver, via which the blade can be reciprocated in oscillating fashion. The nature of the incision cut into the cornea is highly dependent upon providing and preserving a precise cutting edge on the blade, inasmuch as an irregular tissue surface, such as a serrated or torn surface resulting  from the cut, affects both the vision of the patient and the healing process. In addition at least the cutting edge portion of the blade must be assuredly sterile. 
Microkeratome blades are usually used only for a single operation, because of the need for a sharp, uniform cutting edge and the dangers of cross contamination. Prior to use they are conventionally kept in small cases, in sterile condition within an enclosing package. After the sterile package is opened, the blade is withdrawn from its case at the operative site. Prior to extraction of the blade from its case, surgeons often wish to inspect the cutting edge under magnification, and swab the cutting edge to make sure that it is antiseptically clean. The cases heretofore used for these purposes have not permitted complete inspection and treatment of both sides of the cutting edge without removal from the case, and have been structured in such ways as to require special tools or intricate or dexterous manipulation to remove the blade from the case. 